1. Field of the Invention
The present invention relates to a flexible wired circuit board and, more particularly, to a flexible wired circuit board for mounting electronic components thereon.
2. Description of the Prior Art
In recent years, along with the enhancement of high density of electronic components, improvements of the flexible wired circuit board for mounting the electronic components have also been made to have a conductor wiring pattern of finer pitch.
Various attempts have been made for forming a conductor wiring pattern of fine pitch with a high precision. For example, Japanese Laid-open (Unexamined) Patent Publication No. 2000-124580 proposed a method for producing a single-sided flexible printed wiring board in the following steps: (a) a resist pattern corresponding to a wiring pattern is formed on a bottom of a container for forming a polyimide base film, (b) polyamic acid varnish is injected into the container to cover the resist pattern uniformly and then is imidized, whereby a polyimide base film is formed on the resist pattern, (c) the polyimide base film formed on the resist pattern is taken out from the container, (d) the resist pattern is removed from the polyimide base film and a wiring pattern groove is formed in the polyimide base film, and (e) conductive material is disposed in the wiring pattern groove thus formed to thereby form the wiring pattern.
However, this method involves a number of process steps, incurring retardation in improvement of productivity.
Also, along with the progress of the fine-pitch conductor wiring pattern, the conductor wiring pattern is suffering from the disadvantage that defects occur easily, such as, for example, even a minute foreign substance existing between wirings of the conductor wiring pattern may cause a short therebetween easily, causing reduction in yield rates (yielding percentage) of non-defective flexible wired circuit board and eventually causing significant reduction in productivity.